"Stretches into dumb" and "stretches into a growl" are not the same.
I really do sympathize with the frustration about all harsh vocals being called "growls," especially since the way that description gets tossed around here is inaccurate and almost always carries a negative connotation.
In the case of ANtR, though, I really can't blame people for being confused. As Portnoy already stated, his vocal section was originally intended to be growls. And then he dumbed it down to something that sounds like slightly-guttering hollering, only with a growled "roar" at the end, even though he's growled it multiple times on the Black Clouds tour.
The final result is just as mixed as people's perceptions of what it actually is supposed to be. For people who don't listen to growls or harsh music, it comes across as being much greater than the normal Portnoy tough-guy vocals. For people who like growls and harsh music, its too watered down to be impressive.